Auto knapsack



FIG. 1 is a front perspective view of an auto knapsack showing my new design;

FIG. 2 is an enlarged scale right side elevational view thereof;

FIG. 3 is a rear perspective view thereof; and

FIG. 4 is a reduced scale front perspective view thereof shown attached to the rear of a car seat.

The car seat shown in dotted lines in FIG. 4 is for illustrative purposes only and not a part of the design sought to be patented. 

The ornamental design for an auto knapsack, as shown and described. 